A chair is basically made up of a leg body, a seat section that is provided at an upper portion of the leg body, and a back section that supports a user who sits on the seat section. Chairs with various constitutions are generally known.
For example, as a support structure of the back section of the chair, one having a back member and arms that extend upward from a leg body and support portions separated on a back surface of the back member in a width direction from behind is proposed (see Patent Document 1 below).
A chair having a backrest and carrier members supporting respective upper and lower ends in approximately the middle of the backrest in a width direction is also proposed (see Patent Document 2 below).
In the chair, the backrest supported by the carrier members can reliably support the back of a user.
As the back section of the chair, one equipped with a back frame that is supported by a backrest support rod extending from a leg body backward and upward, has an upper frame and a lower frame and is formed in an approximately pentagonal shape when viewed from the front, and an elastically deformable net member that is arranged in the back frame is proposed (see Patent Document 3 below).
In addition, one equipped with a backrest having a back frame including an upper frame section, a lower frame section, a left frame section, and a right frame section and a back plate that is provided on the inside of the back frame, and a back strut supporting the left and right frame sections of the backrest from behind is also proposed (see Patent Document 4 below).